obtaining, from a bitstream, a feature set extracted from an input image using an artificial neural network-based feature extraction method, first information on importance of each of a plurality of channels included in the feature set and second information on a quantization method of the feature set;

decoding the feature set, the first information and the second information; and

dequantizing the decoded feature set based on the decoded first information and the decoded second information,

wherein the second information comprises a number of quantization bits of each of the plurality of channels,

wherein the number of quantization bits is determined based on the importance of each of the plurality of channels,

wherein the first information and the second information have a decoding unit,

wherein the decoding unit is determined to be one of a sequence unit, a group of feature set (GOF) unit, a feature set unit or a channel unit, and

wherein the decoding unit is determined based on data similarity between the feature set and a previous feature set preceding the feature set in decoding order.